bpf: Make bpf_link_fops static

Fix the following sparse warning:

kernel/bpf/syscall.c:2289:30: warning: symbol 'bpf_link_fops' was not declared. Should it be static?

Reported-by: Hulk Robot <[email protected]>
Signed-off-by: Zou Wei <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: SamuelZOU

kernel/bpf/syscall.c

@@ -2283,7 +2283,7 @@ static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
 }
 #endif
 
-const struct file_operations bpf_link_fops = {
+static const struct file_operations bpf_link_fops = {
 #ifdef CONFIG_PROC_FS
 	.show_fdinfo	= bpf_link_show_fdinfo,
 #endif